POP Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

Search Issue | RSS Feeds RSS
Previous Issue Next Issue

Mar 2013

Volume 20, Issue 3, Articles (03xxxx)

Issue Cover Spotlight Figure

Phys. Plasmas 20, 032106 (2013); http://dx.doi.org/10.1063/1.4794320 (10 pages)

M. Raghunathan and R. Ganesh
Enlarge Image | Read More
Return to All Sections
back to top
RSS Feeds
back to top Inertially Confined Plasmas, High Energy Density Plasma Science, Warm Dense Matter

Mixing of equations of state for xenon-deuterium using density functional theory

Rudolph J. Magyar and Thomas R. Mattsson

Phys. Plasmas 20, 032701 (2013); http://dx.doi.org/10.1063/1.4793441 (6 pages)

Online Publication Date: 1 March 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on a theoretical study of equation of state (EOS) properties of fluid and dense plasma mixtures of xenon and deuterium to explore and illustrate the basic physics of the mixing of a light element with a heavy element. Accurate EOS models are crucial to achieve high-fidelity hydrodynamics simulations of many high-energy-density phenomena, for example inertial confinement fusion and strong shock waves. While the EOS is often tabulated for separate species, the equation of state for arbitrary mixtures is generally not available, requiring properties of the mixture to be approximated by combining physical properties of the pure systems. Density functional theory (DFT) at elevated-temperature is used to assess the thermodynamics of the xenon-deuterium mixture at different mass ratios. The DFT simulations are unbiased as to elemental species and therefore provide comparable accuracy when describing total energies, pressures, and other physical properties of mixtures as they do for pure systems. The study focuses on addressing the accuracy of different mixing rules in the temperature range 1000–40 000 K for pressures between 100 and 600 GPa (1–6 Mbar), thus, including the challenging warm dense matter regime of the phase diagram. We find that a mix rule taking into account pressure equilibration between the two species performs very well over the investigated range.
Show PACS
52.25.Kn Thermodynamics of plasmas
52.35.Tc Shock waves and discontinuities
31.15.E- Density-functional theory
28.52.-s Fusion reactors
51.30.+i Thermodynamic properties, equations of state

Experimental investigation of the ribbon-array ablation process

Zhenghong Li, Rongkun Xu, Yanyun Chu, Jianlun Yang, Zeping Xu, Ning Ding, Fan Ye, Faxin Chen, Feibiao Xue, Jiamin Ning, Yi Qin, Shijian Meng, Qingyuan Hu, Fenni Si, Jinghua Feng, et al.

Phys. Plasmas 20, 032702 (2013); http://dx.doi.org/10.1063/1.4794199 (6 pages)

Online Publication Date: 4 March 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ablation processes of ribbon-array loads, as well as wire-array loads for comparison, were investigated on Qiangguang-1 accelerator. The ultraviolet framing images indicate that the ribbon-array loads have stable passages of currents, which produce axially uniform ablated plasma. The end-on x-ray framing camera observed the azimuthally modulated distribution of the early ablated ribbon-array plasma and the shrink process of the x-ray radiation region. Magnetic probes measured the total and precursor currents of ribbon-array and wire-array loads, and there exists no evident difference between the precursor currents of the two types of loads. The proportion of the precursor current to the total current is 15% to 20%, and the start time of the precursor current is about 25 ns later than that of the total current. The melting time of the load material is about 16 ns, when the inward drift velocity of the ablated plasma is taken to be 1.5 × 107 cm/s.
Show PACS
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.70.La X-ray and γ-ray measurements
52.50.-b Plasma production and heating
52.58.Lq Z-pinches, plasma focus, and other pinch devices
52.70.Ds Electric and magnetic measurements

Magnetic field advection in two interpenetrating plasma streams

D. D. Ryutov, N. L. Kugland, M. C. Levy, C. Plechaty, J. S. Ross, and H. S. Park

Phys. Plasmas 20, 032703 (2013); http://dx.doi.org/10.1063/1.4794200 (10 pages) | Cited 1 time

Online Publication Date: 6 March 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Laser-generated colliding plasma streams can serve as a test-bed for the study of various astrophysical phenomena and the general physics of self-organization. For streams of a sufficiently high kinetic energy, collisions between the ions of one stream with the ions of the other stream are negligible, and the streams can penetrate through each other. On the other hand, the intra-stream collisions for high-Mach-number flows can still be very frequent, so that each stream can be described hydrodynamically. This paper presents an analytical study of the effects that these interpenetrating streams have on large-scale magnetic fields either introduced by external coils or generated in the plasma near the laser targets. Specifically, a problem of the frozen-in constraint is assessed and paradoxical features of the field advection in this system are revealed. A possibility of using this system for studies of magnetic reconnection is mentioned.
Show PACS
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.40.Mj Particle beam interactions in plasmas
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions

Hydrodynamic simulations of long-scale-length two-plasmon–decay experiments at the Omega Laser Facility

S. X. Hu (胡素兴), D. T. Michel, D. H. Edgell, D. H. Froula, R. K. Follett, V. N. Goncharov, J. F. Myatt, S. Skupsky, and B. Yaakobi

Phys. Plasmas 20, 032704 (2013); http://dx.doi.org/10.1063/1.4794285 (10 pages) | Cited 1 time

Online Publication Date: 7 March 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Direct-drive–ignition designs with plastic CH ablators create plasmas of long density scale lengths (Ln ≥ 500 μm) at the quarter-critical density (Nqc) region of the driving laser. The two-plasmon–decay (TPD) instability can exceed its threshold in such long-scale-length plasmas (LSPs). To investigate the scaling of TPD-induced hot electrons to laser intensity and plasma conditions, a series of planar experiments have been conducted at the Omega Laser Facility with 2-ns square pulses at the maximum laser energies available on OMEGA and OMEGA EP. Radiation–hydrodynamic simulations have been performed for these LSP experiments using the two-dimensional hydrocode draco. The simulated hydrodynamic evolution of such long-scale-length plasmas has been validated with the time-resolved full-aperture backscattering and Thomson-scattering measurements. draco simulations for CH ablator indicate that (1) ignition-relevant long-scale-length plasmas of Ln approaching ∼400 μm have been created; (2) the density scale length at Nqc scales as Ln(μm) ≃ (RDPP×I1/4/2); and (3) the electron temperature Te at Nqc scales as Te(keV) ≃ 0.95×math, with the incident intensity (I) measured in 1014 W/cm2 for plasmas created on both OMEGA and OMEGA EP configurations with different-sized (RDPP) distributed phase plates. These intensity scalings are in good agreement with the self-similar model predictions. The measured conversion fraction of laser energy into hot electrons fhot is found to have a similar behavior for both configurations: a rapid growth [fhot ≃ fc×(Gc/4)6 for Gc < 4] followed by a saturation of the form, fhot ≃ fc×(Gc/4)1.2 for Gc ≥ 4, with the common wave gain is defined as Gc = 3 × 10−2×IqcLnλ0/Te, where the laser intensity contributing to common-wave gain Iqc, Ln, Te at Nqc, and the laser wavelength λ0 are, respectively, measured in [1014 W/cm2], [μm], [keV], and [μm]. The saturation level fc is observed to be fc ≃ 10–2 at around Gc ≃ 4. The hot-electron temperature scales roughly linear with Gc. Furthermore, to mitigate TPD instability in long-scale-length plasmas, different ablator materials such as saran and aluminum have been investigated on OMEGA EP. Hot-electron generation has been reduced by a factor of 3–10 for saran and aluminum plasmas, compared to the CH case at the same incident laser intensity. draco simulations suggest that saran might be a better ablator for direct-drive–ignition designs as it balances TPD mitigation with an acceptable hydro-efficiency.
Show PACS
52.65.Kj Magnetohydrodynamic and fluid equation
28.52.Cx Fueling, heating and ignition
52.25.Kn Thermodynamics of plasmas
52.40.Mj Particle beam interactions in plasmas
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.57.Fg Implosion symmetry and hydrodynamic instability (Rayleigh-Taylor, Richtmyer-Meshkov, imprint, etc.)

Determination of the inductance of imploding wire array Z-pinches using measurements of load voltage

G. C. Burdiak, S. V. Lebedev, G. N. Hall, A. J. Harvey-Thompson, F. Suzuki-Vidal, G. F. Swadling, E. Khoory, L. Pickworth, S. N. Bland, P. de Grouchy, and J. Skidmore

Phys. Plasmas 20, 032705 (2013); http://dx.doi.org/10.1063/1.4794957 (8 pages)

Online Publication Date: 12 March 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The inductance of imploding cylindrical wire array z-pinches has been determined from measurements of load voltage and current. A thorough analysis method is presented that explains how the load voltage of interest is found from raw signals obtained using a resistive voltage divider. This method is applied to voltage data obtained during z-pinch experiments carried out on the MAGPIE facility (1.4 MA, 240 ns rise-time) in order to calculate the load inductance and thereafter the radial trajectory of the effective current sheath during the snowplough implosion. Voltage and current are monitored very close to the load, allowing these calculations to be carried out without the need for circuit modelling. Measurements give a convergence ratio for the current of between 3.1 and 5.7 at stagnation of the pinch.
Show PACS
52.59.Qy Wire array Z-pinches
52.40.Kh Plasma sheaths
52.80.Qj Explosions; exploding wires
52.70.Ds Electric and magnetic measurements
52.25.Fi Transport properties

Ideal hydrodynamic scaling relations for a stagnated imploding spherical plasma liner formed by an array of merging plasma jets

J. T. Cassibry, M. Stanic, and S. C. Hsu

Phys. Plasmas 20, 032706 (2013); http://dx.doi.org/10.1063/1.4795732 (11 pages)

Online Publication Date: 18 March 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This work presents scaling relations for the peak thermal pressure and stagnation time (over which peak pressure is sustained) for an imploding spherical plasma liner formed by an array of merging plasma jets. Results were derived from three-dimensional (3D) ideal hydrodynamic simulation results obtained using the smoothed particle hydrodynamics code SPHC. The 3D results were compared to equivalent one-dimensional (1D) simulation results. It is found that peak thermal pressure scales linearly with the number of jets and initial jet density and Mach number, quadratically with initial jet radius and velocity, and inversely with the initial jet length and the square of the chamber wall radius. The stagnation time scales approximately as the initial jet length divided by the initial jet velocity. Differences between the 3D and 1D results are attributed to the inclusion of thermal transport, ionization, and perfect symmetry in the 1D simulations. A subset of the results reported here formed the initial design basis for the Plasma Liner Experiment [S. C. Hsu et al., Phys. Plasmas 19, 123514 (2012)].
Show PACS
52.75.-d Plasma devices
52.80.Qj Explosions; exploding wires
52.25.-b Plasma properties
52.25.Fi Transport properties
52.58.-c Other confinement methods
52.65.-y Plasma simulation
Author Select

“Bloch wave” modification of stimulated Raman by stimulated Brillouin scattering

E. S. Dodd, H. X. Vu, D. F. DuBois, and B. Bezzerides

Phys. Plasmas 20, 032707 (2013); http://dx.doi.org/10.1063/1.4796044 (11 pages)

Online Publication Date: 21 March 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Using the reduced-description particle-in-cell (RPIC) method, we study the coupling of backward stimulated Raman scattering (BSRS) and backward stimulated Brillouin scattering (BSBS) in regimes where the reflectivity involves the nonlinear behavior of particles trapped in the daughter plasma waves. The temporal envelope of a Langmuir wave (LW) obeys a Schrödinger equation where the potential is the periodic electron density fluctuation resulting from an ion-acoustic wave (IAW). The BSRS-driven LWs in this case have a Bloch wave structure and a modified dispersion due to the BSBS-driven spatially periodic IAW, which includes frequency band gaps at kLW ∼ kIAW/2 ∼ k0 (kLW, kIAW, and k0 are the wave number of the LW, IAW, and incident pump electromagnetic wave, respectively). This band structure and the associated Bloch wave harmonic components are distinctly observed in RPIC calculations of the electron density fluctuation spectra and this structure may be observable in Thomson scatter. Bloch wave components grow up in the LW spectrum, and are not the result of isolated BSRS. Self-Thomson scattered light from these Bloch wave components can have forward scattering components. The distortion of the LW dispersion curve implies that the usual relationship connecting the frequency shift of the BSRS-scattered light and the density of origin of this light may become inaccurate. The modified LW frequency results in a time-dependent frequency shift that increases as the IAW grows, detunes the BSRS frequency matching condition, and reduces BSRS growth. A dependence of the BSRS reflectivity on the IAW Landau damping results because this damping determines the levels of IAWs. The time-dependent reflectivity in our simulations is characterized by bursts of sub-picosecond pulses of BSRS alternating with multi-ps pulses of BSBS, and BSRS is observed to decline precipitously as soon as SBS begins to grow from low levels. In strong BSBS regimes, the Bloch wave effects in BSRS are strong and temporal anti-correlation with BSRS is due to pump depletion in addition to frequency detuning. In most cases studied, BSBS suppressed the time-averaged reflectivity of BSRS compared to the levels obtained with fixed ions (and therefore no BSBS). The strong spatial modulation of the Bloch Langmuir waves appears to weaken electron trapping and thereby lowers the inflated reflectivity levels of BSRS.
Show PACS
52.38.Bv Rayleigh scattering; stimulated Brillouin and Raman scattering
52.65.Rr Particle-in-cell method
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close